A striking instance of catalysis by alkali metal cations in nucleophilic displacement by alkoxide ion at a phosphinoyl centre in protic media. Though catalysis by divalent cations (Mg2+,Zn-'+,Co2+,etc.) has been observed for a variety of substrates containing specific co-ordination sites, including some with phosphorus functionalities, catalysis by monovalent cations is of much rarer occurrence.